Which of the following is associated with single balanced modulator circuit :
double side band transmission
What a balanced modulator does. It is a multiplier arranged so that the carrier cancels at the output while the sidebands survive. Physically it is two modulator elements (diodes, FETs or a transistor pair) driven in anti-phase by the carrier and in phase by the message, so the carrier terms subtract and the product terms add.
Step 1 — the mathematics of the cancellation. Ordinary AM is
\(s(t)=A_c\left[1+m(t)\right]\cos\omega_c t = A_c\cos\omega_c t + A_c m(t)\cos\omega_c t\)
The first term is the carrier and carries no information; the second holds both sidebands. A balanced modulator removes the first term, leaving
\(s(t)=A_c\,m(t)\cos\omega_c t\)
which is DSB-SC — double sideband, suppressed carrier.
Step 2 — count the sidebands. For a single tone \(m(t)=\cos\omega_m t\), the product-to-sum identity gives
\(A_c\cos\omega_m t\cos\omega_c t=\dfrac{A_c}{2}\cos(\omega_c-\omega_m)t+\dfrac{A_c}{2}\cos(\omega_c+\omega_m)t\)
Two lines survive, one either side of the (absent) carrier — hence double sideband. A single balanced modulator does nothing to remove one of them.
Step 3 — why the other options need extra hardware.
SSB (option 1) needs the DSB-SC output to be passed through a sharp sideband filter, or needs the phase-shift (Hartley) method with two balanced modulators and 90° networks. The balanced modulator alone cannot do it.
VSB (option 3) likewise requires a specially shaped vestigial filter after the modulator, used in analogue television video transmission.
DSB with full carrier (option 4) is exactly what a balanced modulator is designed not to produce — the whole point of balancing is to suppress the carrier, which is where two thirds of the transmitted power would otherwise be wasted.
Single versus double balanced. A single balanced modulator suppresses only the carrier; a double (ring) balanced modulator suppresses both the carrier and the modulating signal, leaving only the sidebands, and is the standard building block of the ring demodulator and mixer.
Hence, a single balanced modulator is associated with double side band transmission.
Similar Questions
Assertion (A) : In amplitude modulation technique the modulation index should be close to 1.
Reason (R) : The power carried by message signal in the side bands increases with increase in modulation index.
Read the statements :
i. DSB has two side bands and SSB has one
ii. DSB has carrier and two side bands and SSB has a carrier and a side band
iii. DSB has carrier and two side bands and SSB without carrier and two different side bands.Which statements are correct ?
Assertion (A) : Amplitude modulation is wastage of power.
Reason (R) : Amplitude modulation is wastage of bandwidth.
The peak carrier voltage is 150 V. If the resistor is 200 Ω and the modulation index is 0.5, the total power in the AM signal is :
The modulation index of an AM wave is given by :
Consider an AM (amplitude modulated) signal
\(s(t) = 20\left[1 + 0.9\cos 2\pi \times 10^4 t\right]\cos 2\pi \times 10^6 t\)
The power efficiency (η) in the AM signal is
In amplitude modulation:
A. Amplitude of carrier is varied by modulating signal
B. Modulation index is between 0 and 1
C. Bandwidth is infinite
D. Bandwidth is twice of minimum modulating frequency.
Choose the correct answer from the options given below:
Match List I with List II
LIST I LIST II A. Power of AM Wave I. \(P_c\left(\frac{m^{2}}{4}\right)\) B. Power of VSB II. \(\frac{m^{2}}{4}P_c+F\left(\frac{m^{2}}{4}P_c\right)\) C. Power of SSB III. \(\frac{m^{2}}{4}\left(\frac{V_c^{2}}{2R}\right)+\frac{m^{2}}{4}\left(\frac{V_c^{2}}{2R}\right)\) D. Power of DSBSC IV. \(\frac{V_{carr}^{2}}{R}+\frac{V_{LSB}^{2}}{R}+\frac{V_{USB}^{2}}{R}\) Choose the correct answer from the options given below:
If 1 MHz carrier is amplitude modulated with a 5 kHz audio signal, the Upper Side Band (USB) and Lower Side Band (LSB) frequencies are ________ respectively.
Important Questions from Amplitude Modulation
The highest modulation frequency typically used in AM broadcast is
Which of the following is NOT the advantage of amplitude modulation?
Bandwidth requirement for Amplitude modulated wave is:
The frequency range of AM radio is:
In an amplitude modulated system, a sinusoidal carrier signal of 1 MHz is modulated by a 10 kHz sinusoidal signal. If the lower sideband and the carrier are suppressed and if the amplitude modulated signal is sampled for further processing, what should be the minimum sampling frequency for baseband sampling?
